For the seek of comparison the same gray image was segmented using original pixels intensities and several clustering approaches: kmeans, hard thresholding using fixed threshold levels equally distributed within range of pixels intensities, multi-level thresholding using Otsu's method [1]}, fuzzy c-means clustering and subtractive clustering [2]}. Fig. REF  presents comparison of the original gray image and its segmentation by enumerated clustering approaches.
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